From Wired:

It sends players out and about in Tokyo searching for virtual treasure by using the GPS technology built into their phones.
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Items like flowers, fruits or creatures are “hidden” around Tokyo, and are visible on a city map on players’ mobile phones. Players form teams, comb the city and try to find each item in various “collections.” They also try to find players from other teams working on different collections with whom to trade.
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“What’s astonishing about Mogi is that it provides a system for people to coordinate and team up and inhabit cities in ways they never have before,” Hall suggests. “It’s dispatching. It’s recreational dispatching, like a cab company, or police or the fire department. It’s fabulously fascinating, this idea that, hey, I’m sitting on my computer at home looking at the Mogi map, and that thing our group wants is over on the west side of town. You’re the closest, so (you go get it) because it’s important for the group.”

From thefeature:

For now, Mogi runs on Japanese carrier KDDI’s phones with built-in GPS capacity.

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Mogi is a collecting game – “item hunt”. The game provides a data-layer over the city of Tokyo. As you move through the city, if you check a map on your mobile phone screen, you’ll see nearby items you can pick up and nearby players you can meet or trade with.

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“some items only appear at certain places, at certain times.” For example, Castelli cites the creatures in the game: “We used the map to give creatures some interesting behavior. Some creatures only hunt at night. Some hang around close to parks.” If a player wants to find that creature, they’ll have to travel near a park[IN THE REAL WORLD] in the evening hours.

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Desktop internet players have access to a larger map. Newt Games’s idea is to have the desktop players guiding the mobile internet players, a goal of collaborative play, team work.

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Players can run around the landscape collecting things, or they can remain in one place and trade with other players.

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Kigen [THE EVENTUAL PRODUCT THAT MOGI IS THE FIRST INSTALLMENT OF] resembles Mogi, with additional layers of complexity added: combat, technological evolution, conquering neighborhoods.